Air curtain

ABSTRACT

An air curtain primarily for use over a doorway has an enclosure containing motor-driven fans for moving air downwardly through the enclosure. The discharging air travels through venturi boxes mounted to pivot about horizontal axes to direct the discharging air. Flexible strips on the venturi boxes abut the enclosure sides to prevent air leakage in any venturi box position. If desired, deflectors are pivotally mounted in the venturi box outlet, and more than one row of venturi boxes may be used.

United States Patent 1191 9/1971 McClurkin 98/ 36 Larson Mar. 19, 1974 [54] CURTAIN I 1 FOREIGN PATENTS OR APPLICATIONS Inventvrl Eugene Larson, Millbraev Calif 564,156 10/1932 Germany; 98/400 [73] Assignee: NPI Corporation, Burlingame, Calif. I

Przmary Eraminer--W1ll1am Wayner 1 Ffled: July 19, 1972 1 Assistant Examiner-William E. Tapolca'i [21] Appl No: 273,121 Attorney, Agent, or Firm-Lothrop & West 1 57 ABSTRACT [52] US. Cl. 98/36, 98/40 N, 415/219 B f h 51 Im. C1 F24f 9/00 FV y W a (way as [58] Field of Search 98/36 40 N 40 C, enclosure contalnmg motor-driven fans for moving air 1 019 SS/DIG downwardly through the enclosure. The discharging air travels through venturi boxes mounted to pivot bout horizontal axes to direct the discharging air. [56] References Cited a Flexible strips on the venturi boxes abut the enclosure UNITED STATES PATENTS sides to prevent air leakage in any venturi box posi- 3.038A00 6/1962 Ruff .L 98/36 ti n If desired, deflectors are pivotally mounted in the y 52/52 venturi box outlet; and more than one row of venturi oysenm 983,877 2/1911 Cummings. 98/36 boxes may be s 3.608.468 3 Claims, 7 Drawing Figures 7 AIR CURTAIN As shown in my U.S. Pat. No. 3,059,563 entitled Air Curtain For Doorways, issued Oct. 23, 1962, there is provided an air curtain according to which a stream of atmospheric air is discharged downwardly over a doorway or comparable opening in order to prevent the ingress of outside contaminants such as insects, dust and the like. While air curtains of the sort disclosed in the patent have been quite successful in most environments, there is nevertheless still an-opportunity to improve their performance and to render them more particularly adapted to special installations.

It is therefore an object of the invention to provide an air curatin that can readily discharge a large quantity of air with a given fan power.

Another object of the invention is to provide an air curtain in which the outflowing air can efficiently be directed as desired.

Another object of the invention is to provide an air curtain with a large through-put of air for the size of the enclosure.

Another object of the invention is in general to provide an improved air curtain.

Other objects,'together with the foregoing, areattained in the embodiment of the invention described in the accompanying description and illustratedin the accompanying drawings, in which:

FIG. 1 is a front elevation of an air curtain pursuant to the present invention, certain interior construction being disclosed by dotted lines;

FIG. 2 is a plan of the structure of FIG. 1, certain screen portions being removed to disclose the interior;

FIG. 3 is an end elevation of the structure of FIG. 1 with interior parts shownin dotted lines;

FIG. 4 is a cross-section, the plane of which is indicated by the .line 4--4 of FIG. 1 and disclosing an end elevation of a venturi box and its attachments;

FIG. 5 is across-section through a venturi box showing the interior construction thereof, portions of the figure being broken away to reduce its size;

FIG. 6 is a plan of a portion of a venturi box, as shown in FIG. 4; and

FIG. 7 is a side elevation of a portion of a venturi box illustrating certain interior deflectors in dotted lines.

While air curtains pursuant to the present invention can be constructed in a widely variant number of ways, the invention has been embodied successfully as shown herein. In this instance, there is afforded an enclosure 6 constructed of the customary angles and channels. The enclosure includes a screen top 7, substantially solid, usually sheet metal end walls 8 and 9 and a back wall 11. This usually is affixed to a wall 12 in which a doorway opening 13 is disposed. This inclosure includes as well a front wall 14, the upper portion of which is somewhat enlarged and is provided with a screen 15 overlying an inlet opening 16 supplementing the top opening 17 normally covered by the screen .7. The lower portion of the front wall 14 is inclined and merges with a discharge duct 18 at the forward portion of the enclosure and a duplicate, parallel discharge duct 19 at the rearward portionof the enclosure.

The ducts 18 and 19 are actually formed by extensions of the end, back and front walls supplemented by a bottom wall 21 which has depending portions 22 and 23 to provide a pairof longitudinally extending, downwardly directed air passages preferably having screen closures 24 across their lower portions. l

Within the enclosure there are disposed propellor motors 26 appropriately mounted in a fashion comparable to that in my above-noted patent and arranged with their rotational axes vertical. While one driving motor can be utilized it is preferred to afford several. In the present instance, the enclsoure contains three substantially identical motors mounted with their axes vertical and evenly spaced. On the shafts 27 of the various motors are air moving fans 28, preferably situated within shroud rings 29. These are fastened to plates, such 21831 and 32, which, in effect, extend entirely across the enclosure and separate the upper and lower portions thereof.

When the motors are energized, air is induced to flow through the screen 7 and through the screen 15 into the upper chamber 33 of the enclosure and then through the shroud rings 29 and into the lower chamber 34 of the enclosure.

Flow from the lower enclosure is through the outlets 18 and 19 under the guidance of venturi boxes 36. A number of venturi boxes are arranged in two parallel rows in the bottom portion of the enclosure. These are all substantially identical so that a description of one applies to the others.

Extending longitudinally or lengthwise of the enclosure, each venturi box includes a pair of side plates 37 and a pair of end plates 38. The configuration is such that the side plates 37 definean upper converging portion 39 and a lower diverging portion41 meeting in a venturi throat portion 42. Substantially on the center line of the venturi throat portion, pivot pins or rods 43 are mounted and are supported on intervening plates 44 spanning the outlets l8. and 19. The venturi boxes, which are somewhat narrower than the outlet openings 22 and 23, can be pivoted or rocked about the pivot pins 43. The direction of the venturi boxes can be inclined toward the opening 13 or away therefrom within a reasonable range.

Since the venturi boxes are not as wide as the housings 22 and 23 and since, therefore, much of the air would bypass the venturi boxes in a fashion not desired, I provide on each of the venturi boxes and particularly attached to the side plates 37 thereof a pair of flexible strips 45. These strips are either metal or plastic having some resiliency. They are arranged with securing pads 46, each directly fastened to the adjacent side plate 37, preferably by welding. The strips atso include diverging wings 47 of sufficient length and flexibility to-abut the adjacent side wall of the outlets 18 or 19, for example, in any rocked or pivoted position of the adjacent venturi boxes. This insures no leakage between the venturi box and its enclosurein any pivoted position thereof. In this fashion, there is afforded an efficient air dis charge mechanism which also can direct the issuing air streams in a selected directionQ s Since it is sometimes desired to direct the outflowing air not straight downwardly, but in an offset direction, we also preferably provide eachof the venturi boxes with a number of deflectors 51. The deflectors are all identical and individually adjustable. Each deflector is a generally planar sheet 52, having edge flanges 53 thereon. The contour of the deflectors preferably corresponds approximately to that of the lower portion 41 of the venturi box within which it is disposed. Mounting each deflector on its adjacent mechanism are pivot pins 54 extending through the flanges 53 and the walls 37. Since these parts are not rectangular, they fit with some frictional interengagement, and the axes of the pins 54 are not quite in line. This means that when the deflectors are moved a moderate amount, they have frictional engagement with the adjacent walls and tend to stay in position despite dislodging forces due to discharge of 5 the air. As shown particularly in FIG. 7, the deflectors can be inclined in any selected direction to divert the outflowing air accordingly.

While there is disclosed herein an arrangement in which two rows of venturi boxes are employed, and in which several venturi boxes are situated in each row, it is of course feasible to provide an arrangement in which but a single row of venturi boxes is employed or v to the upstream side of said fan, means in said enclosure providing on the downstream side of said fan a first air discharge duct having side walls, a venturi box, means for' mounting said venturi box in said duct for pivotal movement toward and away from said walls, and flexible strips extending along and secured to both sides of said venturi box and having wings in abutment with said side walls to preclude air leakage between said venturi box and said side walls.

2. A device as in claim 1 including a deflector within said venturi box, and means for mounting said deflector on said venturi box for swinging movement in a direction at right angles to said pivotal movement of said venturi box.

3. A device as in claim 1 in which said pivotal mounting means supports said venturi box for movement about an axis parallel to said walls and disposed in the throat portion of said venturi box, said venturi box itself has upper wall portions parallel to said walls, and said flexible strips extending from said upper wall portions adjacent'said throat portion in various positions of said venturi box and said axis. 

1. An air curtain comprising an enclosure, a motor-driven fan, means for supporting said fan in said enclosure, means in said enclosure providing an air entrance to the upstream side of said fan, means in said enclosure providing on the downstream side of said fan a first air discharge duct having side walls, a venturi box, means for mounting said venturi box in said duct for pivotal movement toward and away from said walls, and flexible strips extending along and secured to both sides of said venturi box and having wings in abutment with said side walls to preclude air leakage between said venturi box and said side walls.
 2. A device as in claim 1 including a deflector within said venturi box, and means for mounting said deflector on said venturi box for swinging movement in a direction at right angles to said pivotal movement of said venturi box.
 3. A device as in claim 1 in which said pivotal mounting means supports said venturi box for movement about an axis parallel to said walls and disposed in the throat portion of said venturi box, said venturi box itself has upper wall portions parallel to said walls, and said flexible strips extending from said upper wall portions adjacent said throat portion in various positions of said venturi box and said axis. 